Soft Body Object-Collision Object Interaction Not Working
You need to add the Collision physics to the object that yhe soft body should be colliding with, not to the soft body itself. Also, check your normals to ensure they’re pointing ‘outwards’ (otherwise the collision won’t work).

Another issue can be where the Soft Body/Cloth collision ‘Inner’ setting (on the non-soft body mesh) is set too large - it ahould never exceed half the thickness of the mesh or it can have undesired consequences (drawing the soft body through from the ppposite side).

Also, fast moving collisions can potentially get through the surface before they are detected. To address this, increase the Min steps (and Max if you need to increase Min even higher) in the Soft Body Solver settings.



After reviewing the Blend file I noticed that the collision object and the soft body are actually on different layers. For the collision to be active (in fact, for any physics effects) the meshes must share the same layer. To move objects to a different layer you should select them, hit M and click on the desired 'target' layer on the popup panel, holding Shift to select multiple layers if desired. Note that moving layers doesn't necessarily invalidate the soft body cache but this can be triggered by simply selecting the Soft Body object and going into and out of Edit mode (TabTab).